When substances change from one solid phase into another the change is accompanied by absorption or release of heat. The temperature at which such a change takes place is called the transition temperature. This change can be thought of as a change from one compound to another. In this experiment, the compounds used are hydrates(meaning they contain water (H2O) in their chemical formulas) or dehydrates(meaning they do no contain water in their chemical formulas). Hydrates are formed when ionic compounds are formed in water and then isolated as solids, therefore the water remains trapped in the compound. Hydrates are written with a dot between the ionic compound and the amount of water molecules involved with the compound. This indicates the number of water molecules per one molecule of the ionic compound. Though water is involved in the chemical formula, this does not indicate that the substance is wet. In fact, many hydrates have dry appearance and touch. When water is removed from the hydrates, one is left with the anhydrous compound (dehydrate). The mass of a anhydrous compound must be equal to the mass of the original hydrate. When these hydrates are heated (change in temperature), the water will evaporate and thus the compounds will no longer be hydrates. When water vapour is added to the dehydrates, the dehydrates absorb the water vapour to form a hydrate. In this experiment, an attempt will be made to find the transition temperature of 3 specific compounds: Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20), Sodium Sulphate Decahydrate (Na2SO4∙10H2O) and Sodium Acetate Dehydrate (NaCH3COOH). To determine the transition temperatures of the hydrates, the experiment will be done by weighing the compounds at various temperatures. When the mass of the compounds remains the same(stabilizes), it means all the water in the compound has been evaporated, meaning it is no longer a hydrate. Therefore, the temperature at which the mass stabilizes is the transition temperature. To determine the transition temperature of the dehydrates, water in the form of water vapour is added and the temperature at which the dehydrates becomes hydrates is detected.
TRANSITION TEMPERATURES FOR SODIUM THIOSULPHATE PENTAHYDRATE AND SODIUM SULPHATE DECA HYDRATE
1) Wear safety goggles and gloves.
2) Set up a retort stand and clamp a ring clamp 30 cm above the base.
3) Place a piece of wire gauze on the ring clamp so that the wire gauze fully covers the clamp.
4) Place a Bunsen burner beneath the clamp.
5) Place 50 mL of Sodium Thiosulphate Pentahydrate into a 250 mL beaker.
6) Place a thermometer into the compound in the beaker. Record the temperature and remove thermometer.
7) Weigh the beaker and list the compound’s physical properties of weight, colour and other noticeable observations at the certain temperature. Mass will be measured with use of a electronic scale.
8) Ignite the Bunsen burner with a flint lighter and adjust to a moderate flame.
9) Using beaker tongs, place the beaker with the Sodium Thiosulphate Pentahydrate on the wire gauze.
10) Place the thermometer into the compound. At increments of 5 degrees Celsius, carefully remove beaker with beaker tongs.
11) Record the temperature and remove thermometer.
12) Weigh beaker and record mass, colour and other noticeable changes quickly.
13) Using beaker tongs, place the beaker on the wire gauze again.
14) Repeat steps 9-11 until the mass of the beaker stabilizes or stays the same.
15) When the mass of the beaker stabilizes, turn off the Bunsen burner.
16) Empty the contents of the beaker safely and wash the beaker.
17) Repeat steps 4-14 but instead of using 50 mL of Sodium Thiosulphate Pentahydrate, use 50 mL of Sodium Sulphate Deca Hydrate.
TRANSITION TEMPERATURES FOR SODIUM ACETATE DEHYDRATE
Place 100 mL of water into a beaker and place onto a hot plate.
Place 50 mL of crushed Sodium Acetate Dehydrate into a petri dish next to the hot plate.
Measure the mass of the petri dish filled with Sodium Acetate Dehydrate.
Place a thermometer into the petri dish so that bulb of thermometer touches the compound.
Turn on hot plate and heat until water boils.
Cover all items with a glass cover until the Sodium Acetate Dehydrate absorbs the water vapour and all the water evaporates.
Record all noticeable changes.
Remove glass cover.
Weigh the mass of the petri dish.
Empty contents of petri dish safely and wash all utensils.
Sodium Thiosulphate Pentahydrate is slightly toxic and harmful to skin. It is an eye irritant and can cause health complications if ingested. It is incompatible with acids and oxidizing agents. Handle with care.
Sodium Sulfate Decahydrate may be corrosive and is a mild eye irritant. It may explode if overheated. Handle with care.
Sodium Acetate Trihydrate, from which third compound is made, is a skin and eye irritant. Handle with care.
When using a Bunsen burner make sure flammable materials do not surround the burner's area. Make sure you wear safety goggles. After the material has been heated, wait several minutes before grasping it always with gloves. Use beaker tongs, ring stand and wire gauze where required.
Take care to not expose thermometer to flame as this will cause an explosion.
When finished with the burner, turn gas off completely.
General Safety Rules
Safety goggles must be worn at all times (contact lenses should not be worn).
Long hair must be tied back and loose clothing must be secured.
Do not consume any of the hydrates and other materials used in the experiment.
Gloves must be worn at all times when handling hot materials.
Take extra care when using the heating pad to avoid burning- if skin is burnt, rinse under cold water.
If mercury is spilled from the thermometer, notify a teacher immediately. Do not try to clean it up yourself.
Report all breakages of beakers to the teacher. Broken glassware and glassware with sharp edges must be repaired or disposed of properly. Be sure that all glass splinters are swept up and placed in the broken glass container.
Wash your hands when handling chemicals
Avoid transporting chemicals through congested areas.
Clean up carefully- sink drains must be thoroughly flushed during the disposing of chemicals.
Make sure you know where the fire extinguisher, chemical shower and eye wash station are, in case of an emergency.
Sources of Experimental Error
The results of this experiment could be erroneous for a number of reasons. The first being that recording of noticeable characteristics will not be done quickly enough, and this will result in an incorrect transition temperature because at the time when the flame was at the actual transition temperature, the experimenter may still be recording.
The second source of error may come from the measurement of the temperature with the thermometer. If the sample size of the compound is not big enough, the thermometer bulb will not be covered and the temperature measured will be inaccurate.
Observations
Data Table
Calculations
Result
Discussion
Conclusion
Superconductivity
Superconductivity is a phenomenon occurring in certain substances generally at very low temperatures. They are characterized by their exact zero electrical resistance and their exclusion of the interior magnetic field (the Meisnner effect). PROPERTIES OF SUPERCONDUCTORS Physical properties of superconductors that vary for each material include: heat capacity, critical temperature, critical field, and critical current density. However, the physical property that must stay consistent in all superconductors is their exact zero resistance of electricity. NORMAL CONDUCTOR vs. SUPER CONDUCTOR A normal conductor is electric resistant. In a normal conductor, the current occurs as a “fluid of electrons” moving across a heavy ionic lattice. The electrons constantly collide with the ions in the lattice. During this collision, energy is carried by the current and absorbed by the lattice and converted to heat. This heat is known as the vibrational kinetic energy of lattice ions. A superconductor has zero electric resistance. In a superconductor, the electronic fluid cannot be resolved in individual electrons. Instead, it consists of electrons known as Cooper pairs. Cooper pairs are caused by the attractive force between electrons from the exchange of phonons. CALCULATING ZERO RESISTIVITY If the voltage is zero, then the electric resistance is zero. The simplest method to measure electrical resistance of a sample is placing it in an electric circuit in a series with current source I, and measuring the resulting voltage V. The resistance is given by Ohmn’s law (R = V/I) MEISNNER EFFECT The Meissner Effect is the expulsion of a magnetic field from a superconductor. When a superconductor is placed in a weak external magnetic field H, it penetrates the superconductor a very small distance λ, called the London penetration depth. This decays exponentially to 0 within the bulk of the material. The Meissner effect breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs: Type 1 and Type 2.
Completed Project
DETERMINING TRANSITION TEMPERATURE OF HYDRATES
Comment: you may want to measure the temperature at which the water of hydration is lost using a boiling tube (large test tube) and use solid saltsIntroduction
Transition Temperature of Hydrates
When substances change from one solid phase into another the change is accompanied by absorption or release of heat. The temperature at which such a change takes place is called the transition temperature. This change can be thought of as a change from one compound to another. In this experiment, the compounds used are hydrates(meaning they contain water (H2O) in their chemical formulas) or dehydrates(meaning they do no contain water in their chemical formulas). Hydrates are formed when ionic compounds are formed in water and then isolated as solids, therefore the water remains trapped in the compound. Hydrates are written with a dot between the ionic compound and the amount of water molecules involved with the compound. This indicates the number of water molecules per one molecule of the ionic compound. Though water is involved in the chemical formula, this does not indicate that the substance is wet. In fact, many hydrates have dry appearance and touch. When water is removed from the hydrates, one is left with the anhydrous compound (dehydrate). The mass of a anhydrous compound must be equal to the mass of the original hydrate. When these hydrates are heated (change in temperature), the water will evaporate and thus the compounds will no longer be hydrates. When water vapour is added to the dehydrates, the dehydrates absorb the water vapour to form a hydrate.
In this experiment, an attempt will be made to find the transition temperature of 3 specific compounds: Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20), Sodium Sulphate Decahydrate (Na2SO4∙10H2O) and Sodium Acetate Dehydrate (NaCH3COOH). To determine the transition temperatures of the hydrates, the experiment will be done by weighing the compounds at various temperatures. When the mass of the compounds remains the same(stabilizes), it means all the water in the compound has been evaporated, meaning it is no longer a hydrate. Therefore, the temperature at which the mass stabilizes is the transition temperature. To determine the transition temperature of the dehydrates, water in the form of water vapour is added and the temperature at which the dehydrates becomes hydrates is detected.
Materials
Procedure
TRANSITION TEMPERATURES FOR SODIUM THIOSULPHATE PENTAHYDRATE AND SODIUM SULPHATE DECA HYDRATE
1) Wear safety goggles and gloves.
2) Set up a retort stand and clamp a ring clamp 30 cm above the base.
3) Place a piece of wire gauze on the ring clamp so that the wire gauze fully covers the clamp.
4) Place a Bunsen burner beneath the clamp.
5) Place 50 mL of Sodium Thiosulphate Pentahydrate into a 250 mL beaker.
6) Place a thermometer into the compound in the beaker. Record the temperature and remove thermometer.
7) Weigh the beaker and list the compound’s physical properties of weight, colour and other noticeable observations at the certain temperature. Mass will be measured with use of a electronic scale.
8) Ignite the Bunsen burner with a flint lighter and adjust to a moderate flame.
9) Using beaker tongs, place the beaker with the Sodium Thiosulphate Pentahydrate on the wire gauze.
10) Place the thermometer into the compound. At increments of 5 degrees Celsius, carefully remove beaker with beaker tongs.
11) Record the temperature and remove thermometer.
12) Weigh beaker and record mass, colour and other noticeable changes quickly.
13) Using beaker tongs, place the beaker on the wire gauze again.
14) Repeat steps 9-11 until the mass of the beaker stabilizes or stays the same.
15) When the mass of the beaker stabilizes, turn off the Bunsen burner.
16) Empty the contents of the beaker safely and wash the beaker.
17) Repeat steps 4-14 but instead of using 50 mL of Sodium Thiosulphate Pentahydrate, use 50 mL of Sodium Sulphate Deca Hydrate.
TRANSITION TEMPERATURES FOR SODIUM ACETATE DEHYDRATE
Safety Precautions
Safety for Experiment
General Safety Rules
Sources of Experimental Error
The results of this experiment could be erroneous for a number of reasons. The first being that recording of noticeable characteristics will not be done quickly enough, and this will result in an incorrect transition temperature because at the time when the flame was at the actual transition temperature, the experimenter may still be recording.
The second source of error may come from the measurement of the temperature with the thermometer. If the sample size of the compound is not big enough, the thermometer bulb will not be covered and the temperature measured will be inaccurate.
Observations
Data Table
Calculations
Result
Discussion
Conclusion
Superconductivity
Superconductivity is a phenomenon occurring in certain substances generally at very low temperatures . They are characterized by their exact zero electrical resistance and their exclusion of the interior magnetic field (the Meisnner effect ).
PROPERTIES OF SUPERCONDUCTORS
Physical properties of superconductors that vary for each material include: heat capacity, critical temperature, critical field, and critical current density. However, the physical property that must stay consistent in all superconductors is their exact zero resistance of electricity.
NORMAL CONDUCTOR vs. SUPER CONDUCTOR
A normal conductor is electric resistant. In a normal conductor, the current occurs as a “fluid of electrons” moving across a heavy ionic lattice. The electrons constantly collide with the ions in the lattice. During this collision, energy is carried by the current and absorbed by the lattice and converted to heat. This heat is known as the vibrational kinetic energy of lattice ions.
A superconductor has zero electric resistance. In a superconductor, the electronic fluid cannot be resolved in individual electrons. Instead, it consists of electrons known as Cooper pairs. Cooper pairs are caused by the attractive force between electrons from the exchange of phonons.
CALCULATING ZERO RESISTIVITY
If the voltage is zero, then the electric resistance is zero. The simplest method to measure electrical resistance of a sample is placing it in an electric circuit in a series with current source I, and measuring the resulting voltage V. The resistance is given by Ohmn’s law (R = V/I)
MEISNNER EFFECT
The Meissner Effect is the expulsion of a magnetic field from a superconductor. When a superconductor is placed in a weak external magnetic field H, it penetrates the superconductor a very small distance λ, called the London penetration depth. This decays exponentially to 0 within the bulk of the material. The Meissner effect breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs: Type 1 and Type 2.
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